This invention relates generally to radiation detectors and specifically to an apparatus and method for measuring the amount of impinging radiation which is reflected from the detector surface.
The absolute measurement of the radiation striking a detector depends upon what portion of that radiation is absorbed. If no radiation were reflected, the detector would react to the entire impinging radiation and its measurement would be an indication of the total radiant energy. However, all detectors cause some reflections and, to the extent that they do, the readings they yield are inaccurate. Since the reflectance and absorptivity of any material varies with the type of radiation to which it is subjected, it is imperative for accurate measurements to evaluate the absorptivity of such radiation detectors in regard to the particular radiation of interest.
The requirement is for a convenient system for calibration of radiation detectors to an accepted secondary standard so that measurements taken with such detectors may be adjusted to account for the radiation which is reflected from the surface of the detector and which has no effect on the reading given by the detector. Such a calibration must be applicable to the particular radiation for which the detector is used but need not be an absolute measurement. The specific requirement is that the calibration system yield a reading of the relationship of reflected or absorbed radiation to the total applied radiation which may then be applied to modify the output readings of the detector.
The present invention provides an accurate and convenient apparatus and method for the calibration of the absorptivity of radiation detectors which may be used for any type of radiation and with all detectors.